LSW: Properly set page transition and cleanup definitions on the way

Set slide animation by default and use it in all pages.
Fix wrong/missing slide animations on various transitions like WiFi
and the backup subpage.

Change-Id: I78c87f38eb615379d39c89b43a016ed2ffb98695

src/org/lineageos/setupwizard/BaseSetupWizardActivity.java

@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2016 The CyanogenMod Project
- * Copyright (C) 2017 The LineageOS Project
+ * Copyright (C) 2017-2020 The LineageOS Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -89,7 +89,7 @@ public abstract class BaseSetupWizardActivity extends Activity implements Naviga
     private boolean mIsFirstRun = true;
     protected boolean mIsGoingBack = false;
     private boolean mIsPrimaryUser;
-    private int mResultCode = 0;
+    protected int mResultCode = 0;
     private Intent mResultData;
 
     @Override
@@ -520,7 +520,7 @@ public abstract class BaseSetupWizardActivity extends Activity implements Naviga
     }
 
     protected int getTransition() {
-        return TRANSITION_ID_DEFAULT;
+        return TRANSITION_ID_SLIDE;
     }
 
     protected boolean tryEnablingWifi() {